1. Field of the Invention
The present invention relates generally to the field of control systems for hydraulic presses, and more particularly to an improved control system which is particularly suited for use with a hydraulic punch press to reduce the release impact of the punch as it exits a workpiece.
2. Description of the Prior Art
Workpieces, such as sheet metal, are commonly punched or stamped by hydraulic presses. Relatively great forces between the punch and bottom die occur as the punch moves through the workpiece. These forces produce correspondingly large deformation energies in the workpiece and press, and particularly in the hydraulic fluid of the activating cylinder. These deformation energies are released suddenly as the tool passes through the workpiece in such a way that they suddenly accelerate the punch, thereby creating objectionable noise and strain on the press.
To cushion or dampen this "release impact", it is known to provide shock-absorbing elements on the press to cushion the sudden release of the ram when the punch exits the workpiece. It is also known to provide such damping elements on the tool itself. The use of these damping elements is somewhat complex, and it is difficult to adjust the point of engagement, especially when a plurality of such elements are employed. Moreover, these damping elements must be changed or adjusted every time the tool is changed.